Master cylinder for brakes



R. A. GOEPFRICH Nov. 1s? I194.1.

` MASTER CYLINRER RoR BRAKES Fie'd March 10, 1938 2 Sheets-Sheet l IDW INVENTOR f/vof/f/CH l 1'54 #wig/M46 A TTORNE'Y INov. 18, 19411. Y R. A. GoEPFRlcH r E 21,262,843

MASTER CYLINDER EOE BRAKES Filed March 1o, l1933 2 sheets-Sheng ATTORNEY Patented Fav. 18, 1941 UNITED STATES PATENT OFFICE MASTER CYLINDER Foa BRAKES nudolph'A. Gpfrich, south Bend, ma., assignor 4 to Bendix Products Ind., a corporation o 4 Claims.

This invention relates to braking systems of the hydraulic or fluid pressure type and more particularly to devices f or producing fluid pressure to operate suela.' braking systems.

In conventioz al fluid braking systems, the cylinder of the fluid pressure producing device is generally connected to the fluid reservoir by two ports known in the art as the supply port and the compensating port. The latter (compensating) port is usually located so that when the piston is in its maximum retracted position, Athe port is -slightly ahead of a flexible cup seated on the pistonahead. As the piston travelsfon its compression stroke the resultant pressure at the head of the piston extends the flexible cup. This expansion of the cup retards the travel of the piston as the cup passes the compensating port. Sometimes the movement past the port even tears the cup. It is the aim of the invention of my copending application Serial No. 107,239, filed October 23, 1936 issued on June 27, 1939, as Patent No. 2,163,- 874, and also the object of the invention disclosed herein, to overcome this undesirable condition. Application Serial No. 371,074, filed December 2l, 1940 is a division of this application.

An object, therefore, 'of this invention is to provide a fluid pressure producing device wherein the cylinder is constructed in such a vmanner as to obviate any vundesirable opening into the fluid reservoir tending to be injurious to the piston cup.

A further object of the invention is to provide a fluid pressure producing device having a novel piston permitting by-passing of fluid from the reservoir through itself when the piston is in its retracted position, or during its retracting stroke.

Corporation, South Bend,

f Indiana Application March 10, 1938, vSerial No. 195,021

(Cl. (S-54.6)

A still further object of this invention is to provide a substantially shorter piston of this type than pistons heretofore proposed or used.

Such a, piston is simpler in construction, the cylinder bore required is relatively shorter, and the entire fluid pressure producing device consequently takes up less space in the vehicle with the added feature of ease of construction of the entire unit at a substantially vreduced cost of manufacture.

Other objects and desirable particular constructions and arrangement ol.' parts will become apparent upon reference to the following detailed description of the three illustrative embodiments shown in the accompanying drawings, in which:

Figure 1 -is a diagrammatic illustration of a fluid brake system embodying myinvention;

Figure 2 is a side elevational view in section of 'my novel vertical master cylinder showing Vthe ing amodification of the piston and piston valve of Figure 2; and

Figure 4 is a view in section showing a further modification of my invention as embodied in a horizontal master cylinder.

Reference is made to the drawings for a more detailed description and particularly to Figure 2 which shows the preferred form of my invention constituting a vertical master cylinder.

My novel vertical master cylinder is shown in-Y corporated with a general braking system for a vehicle in Figure l. As illustrated my master cylinder is indicated generally by the reference-'numeral I0 having a fluid reservoir I2, a depending cylinder I4 in axial alignment and communicating with the reservoir, and a flexible boot I8 sleeved about the rod I6.

' The rod I6 has attached to itself at its free end the clevis 20 to which is pivotally connected a foot pedal 22 pivoted on a xed Support 24 and having a retractile spring 26 also connected to a xed support. As pressure is applied to the -foot pedal 22 the force is transmitted to the clevis 20 actuating the rod I6 causing the consequent application of the brakes to the system in a manner to be hereinafter more fully described.

The depending cylinder I4 has both of'its ends threaded externally, the upper end being threaded the other receiving ra vcap 28 having a central Vthreaded bore communicating with the inner portion of the cylinder and forming the discharge port 30 therefor.

A fluid pressure delivery pipe 32 suitably connected to the discharge port `30 of the master cylinder I0 has conduits connected respectively to fluid pressurev actuated motors 34 arranged in` pairs; one pair for the actuation of the brakes associated'with the front wheels of the vehicle, and the other for actuation of the brakes-.associated With lthe rear wheels o f the vehicle. f y

The brakes may be of the standard type each including a fixed support or backing plate 36, a rotatable drum 38 associated with the backing plate, a pair Aof corresponding brake shoes 4U and 42 pivoted on the backing plate, and pressure Ihe fluid reservoir I2 is provided with a lling per end a substantially decreased extending hollow cylindrical portion adapted to receive the rod i I8 and ending in a slightly increased outwardly flanged portion or shoulder 4 8. The latter acts as an abutment for the retainer of one end of the flexible boot I8 having its other endvsecurely fastened about the clevis 28. Also formed integrally Swith the boot I8 is a coaxially mounted baille 52 surrounding the rod I8 giving a seal-tight t and having an atmospheric vent 54 communicating `with another vent 56 of the boot and with the Iiiuid reservoir.

The vertical rod I6 extends into the reservoir I2 at `its central axis; The rod carries below the baille 52 another circular baille 58 so designed `that when the system is in its ,normal rest position the baille 58 will rest below the top open end Iof the reservoir thus defining a chamber which retards the resultant splashing of the iluid when the rod I8 is returning to its normal rest position Isubsequen to the releasing of the foot pedal.

The cyl nder I4 has a reciprocable piston 58 having a substantially decreased slightly extendl ing portion at its rear carrying/a recess 88 adapted to receive the ball 82 formed on the lower end l rests against a Washer 64 having a central open-.

of the rod I8. 'I'he ball is suitably secured in the socketlor recess so that the rod and piston may move in unison. Y

In its retracted or rest position .the piston 58 ing forming an annular recess'86 communicating 1 with the by-pass passage 12 of the piston through angular passages I4.

The head of the piston 58 is formed with a frustro-conical recess 18 and the by-pass 'I2 communicating with the angular' passages 14. These 1 latter passages communicate with the fluid reservoir I2 by virtue of the annular passage 88 formed by the washer 84 and the rear body portion of the piston 58.

The head of the piston s 1s provided with a.

` rubber cup 18 having slightly outwardly daring lips or anges 88 which upon the compression stroke tend to distend against the inner walls of the cylinder I4 so as to provide a seal-tight t prohibiting the escape of any of the fluid upon such compression stroke.

Formed to nt within the-frustro-conical 're- 1 cess 18 of the piston 58 is a, valve 82 having slid- `.able stem 84 in the by-pass passage12. The stem `is suitably channeled so as to providefor the Y.

free flow of fluid through the by-pass "I2 to the head of the cylinder |74 and islongitudinally slotted for the reception of a retaining pin 88.

One of the angular passages( 14 in the rear of f ton head.

The head of the valve 82 has an extension 88 and'a leak-proof washer 98 sleeved on the extension and retained against displacement by the f extension and has a rim conforming to the wall of the frusto-conical recess 18 so as to 'effectively seal the valve when it is in its closed position on the compression stroke. Aiding its closure is also provided a light spring 82 resting against the `openingreceiving the plug 48 andhas at its upextension 88 at one end and the head of the cylinder I4 at its other end.

The valve 82 is formed 'with a conical metallic 'head 9 4 arranged to contact the frustro-conical recess 18` and form a primary seal thus relieving the rubber washer 88 of cutting pressure.

In its operation as the foot pedal lever 22 is depressed, the force is transmitted through the clevis 28 to the rod I8 which in turn starts the piston 58 on its compression stroke. The pressure created by the iiuid at the head of tlie piston 5 8 with the aid of the spring 92 retains the valve 82 in its seat prohibiting any back iiow.

" The compression stroke of the piston is rlimited stroke causes now of uid through the' discharge port 38 to the conduits 82 and into the motors 34 causing the movement of the shoes 48 and 42 against the force of the retractile spring 44.

As the foot pedal 22 is released the rod i8 and piston 58 travel to their retracted position. The retaining pin 88 holds the valve 82 andV avoids complete displacement should vacuum be created on the upward stroke at the head of the piston. As the piston reaches its maximum retracted p0- sition, the pin I6-at its rear contacts the stem 84 of the valve tripping it oi its seat to permit inilow of iiuid from the reservoir should any have been lost in the system during the compression stroke.

In the modiiication of Figure 3, the piston |58 has a decreased circumferential portion at its head receiving the rubber washer 88 having lips 88 which spread against the walls of the cylinder I I4 upon the compression strokeproviding a sealtight nt against any back-now.

The frustro-conical recess |18 in the head of the piston |58 receives the valve |82 having the st em |84 slidable in the by-pass passage |12 and having a longitudinally slotted extended portion |88 receiving the retaining pin |82 passing through the cylinder I|4. The stem |84 is also longitudinally slotted to receive a retaining pin |88.

'The function ofthese pins is such that upon the compression stroke, the valve |82 is seated in the conical recess of the piston head. Its tripf ping occurs when upon the return stroke the pin |82 seats at the end of the longitudinal slot of the extension |88. The latter is so designed that upon reaching the retracted position the valve |82 is held slightly from its seat in the piston head permitting communication of the reservoir with'the cylinder head. The pin |88 on the other hand performs the function of carrying the valve |82 with the piston on the return stroke prohibiting entire displacement of the valve resultingof vacuum created by the retracting piston.

In all other respects the device functions in the same manner as that of Figure 2 before described. y

In the modication shown in Figure 4, there is shown a horizontal master cylinder having a cylinder ||0 formed with a discharge port H2, the cylinder being integrally formed with the Huid reservoir IIB which has the vent plug I I8 for filling.

The cylinder `II8 receives a reciprocable piston |28 suitably connected to a rod |22 having at one of its ends a ball |24 fitted in a recess |26 at the rear of the piston and a clevis |28 at its other `end.

and suitably fastened tu the cylinder at one end and to the clevis |20 at the other end is provided to retain fluid therein and to be retractible with the rod |22.

The iluid reservoir IIB has a communication port |32 receiving a ported plug |34 extending into the cylinder H0.

The piston |20 is constructed with a grooved cutaway portion about its inner periphery so as to receive the rubber washer having lips which upon the compression stroke distend so as to' insure a seal-tight closure for the piston.

The piston further has a passage |30 formed angularly so as to receive the slidable grooved stem |40 of the conical valve |42 seated in the angular conical recess |44 of the piston head. The stem |40 is provided with a longitudinal slot adapted to receive a retaining pin |40.

The rear of the piston ||8 is provided with a cut-away portion so as to permit the travel of the piston without interference-oi the extending channeled plug |34, and to permit communication oi the reservoir I6 withthe hollow boot |30. The rear of the piston is secured'against rearward displacement by the washer |40 and split spring |50.

'I'he channeled plug |34 serves the double purpose oi' acting as a communication port and as a Atripping member for the valve |42 whenthe piston is in its maximum retracted position to @compensate for any iluid that may have been lost throughout the system during the braking thereot.

In its operation this master cylinder is similar to that described in the preferred embodiment.

With the actuation of the foot pedal 22, thepiston ||0 is sent on its compression stroke causing discharge of iluid through discharge port ||2 to the system as shown in Figure l.

While three illustrative embodiments have been described in detail, it is not my intention to limit the scope of the invention to those particular embodiments. ,or otherwise than by the terms oi' the appended claims.

1'.A master cylinder having a piston formed with a passage therethrough and with a conical recess in its 'face into which said passage opens, a valve having a conical head adapted to seat vinsaidrecessandasealcarrieilbysaidhead and adapted to seal against the wall oi' said recessand .having a stem extending into said passage, means comprising apin extending obliquely through said piston for opening said valve and means tor operating said piston having a ball I and socket connection with said piston concencentric recess in its face into which said passage` opens and from which said passage runs to a point on the upper face oi said piston eccentric l5 said piston.

thereof, a valve having a head adapted to seat in said recess and a seal carried by said head and adapted to seal against the wall of said recess and having a stem extending into said recess, and means comprising a pin secured in said recess in said piston engaging a slot in'said stem and preventing complete separation of said valve from said piston, in combination withv stop means acting on said stem when the piston vis retracted to unseat said valve.

3. A master cylinder having a piston'formed with a concentric passage therein and. with a concentric conical recess in its face into which said passage opens, a valve having a conical head adapted to seat in said recess and a seal carried by said head and adapted to seal against the-walliof said recess and having a stem extending into said concentric passage. and means engaging said stem and preventing complete separation of said valve from said piston, in combination with an eccentric stop, a pin positioned in an oblique bore in said piston contacting with said stop at times and said `pin acting on said stem in said concentric passage when the piston is retracted to unseat said valve.

4. A master cylinder having'a piston formed with a concentric passage therethrough and with a conical recess in its face into which said passage opens, havingv also an oblique ,e leading from said concentric e, a .valve having a conical head adapted to seat in said recess and a seal carried by said head and adapted to seal against the wall of said recess and having a stem extending into said concentric passage and means in said concentric passage engaging said stem and preventing complete separation of said valve from said piston, in combination with a stop and pin associated therewith acting on said when the piston is retracted to unseat said valve', and in combination with a piston rod connected by a concentric balk and socket connection with RUDOLPH A. common. 

